It is important that a reactor containing an exothermic reaction be cooled for safety reasons as well as to ensure that the reaction proceeds efficiently. Cooling is generally carried out by indirect heat exchange such as by maintaining the reactor in a water bath or in a cooling jacket.
Direct heat exchange, wherein the cooling fluid directly contacts the contents of the reactor, is more efficient than indirect heat exchange but may be disadvantageous because the contact of the cooling fluid with the reactants may adulterate or otherwise harm the product.
Cryogenic liquids contain a large amount of refrigeration and might be useful for direct contact cooling of an exothermic reactor owing to the chemical inertness of many cryogenic liquids. However, because of the extremely cold temperatures characteristic of cryogenic liquids, freezing of the reactants, solvents and/or products of the reaction onto the injection device which provides the cryogenic liquid into the reactor vessel creates a danger that the flow of cryogenic liquid into the reactor vessel will slow or stop altogether. This will result in a runaway reaction with catastrophic consequences. Thus, the considerable potential advantages of using a cryogenic liquid to cool an exothermic reaction by direct contact have not been realized.
Accordingly, it is an object of this invention to provide a system which enables one to effectively employ a cryogenic liquid to cool a reactor containing an exothermic reaction by directly contacting the contents of the reactor with cryogenic liquid.